It is already known to use a suction device to displace a thread, especially in stretch-winding machines in which a thread, usually comprised of a multiplicity of filaments and of a synthetic resin material, is subjected to thermal treatment and stretching and then is wound up into a yarn package or bobbin on a winding sleeve or tube, preferably in a cross-winding operation wherein the turns of one layer are oriented with an opposite inclination from the turns of another, i.e. are pitched oppositely to the winding stations. The winding stations are provided with winding units each of which can include a rotatable winding sleeve, a friction roller which bears against the outer periphery of the winding sleeve and the layers of the thread wound thereon, a cross-winding box or device for generating the different orientations of the turns of the layers and a spool holder and a spool carriage.
The full spools, following completion of a winding operation, must be replaced by winding sleeves or tubes. This replacement can be carried out automatically or manually and, in the case of manual replacement, it is necessary that the thread be engaged, usually by a suction device, for example a suction gun, and carried to the winding sleeve at which the thread is then engaged by the winding sleeve.
For effective engagement of the thread, the winding sleeve can be formed with a V-shaped thread-capture slit which can extend over part of the periphery of the winding sleeve at an end region thereof.
The application of the thread to a stretch-winding machine generally has required heretofore the following steps:
The thread which is to be picked up is removed by means of a suction device from a supply station (usually a bobbin in a creel) and fed via a thread-monitoring device or thread-separating device to a supply cylinder. From this cylinder it is passed around at least one and preferably two or three gallets (e.g. an input gallet, a preheating gallet, a fixing gallet and a feed or supply gallet) and the associated transfer rollers. Between the individual gallets, working elements, for example heating devices such as plate heaters can be provided. The thread is then supplied via the cross-winding mechanism to the V-shaped thread-capture slit of the winding sleeve as close as possible to the contact line with which the friction roller engages the winding sleeve. The thread-capture slit engages the thread and tears the latter in a controlled manner. The length thread fed by the supply or feed gallet is wound on the winding sleeve.
In practice, this system has a number of problems, especially with respect to the tearing of the thread. If the thread is a high-strength material, the tearing or rupture of the thread requires relatively high tearing force. This tearing force can have the effect of briefly reducing the speed of the winding sleeve driven by the friction roller. This in turn can loosen the thread reserve and the first few windings or turns of the thread on the winding sleeve. The result is a reduction in quality of the spool. The thread breakage is generally carried out in the region of the suction device, i.e. in the region of the suction gun.
Furthermore, the length of the thread end is not controllable. This uncontrollable length, which can be between 10 and 30 cm depending upon the type of system used to apply the thread to the winding sleeve (and in the case of a suction gun) to a meter or more as is the case with an applicator tube with a stationary injector as the suction device, gives rise to a significant quality problem. Slack loops on the winding sleeve can catch impurities and contaminants like lint and excessively long thread ends can be bound in an uncontrollable manner in the body of the bobbin or yarn package.